Department of Applied Mathematics, Research School of Physics and Engineering, Australian National University, Canberra 0200 ACT, Australia.
J Phys Chem B. 2010 Nov 25;114(46):14977-82. doi: 10.1021/jp107224r. Epub 2010 Oct 28.
The adsorption of nonionic surfactants to the silica-water and cellulose-water interfaces was studied using optical reflectometry (OR) and soft-contact atomic force microscopy imaging. The polyethylene oxide alkyl ethers C(14)E(6) and C(16)E(8) were shown to readily adsorb to both interfaces. The kinetics of the adsorption process as well as the equilibrium surface excess was determined using OR. In agreement with previous studies, the short headgroup surfactant C(14)E(6) adsorbed to a greater extent than the longer headgroup surfactant C(16)E(8) on silica. This trend was also observed for the cellulose-water interface. The structure of the adsorbed surfactant layer above the critical surface aggregation concentration (csac) was visualized using the soft contact imaging technique for both interfaces. On the silica surface, the layer structure for both surfactants mostly showed spherical aggregates, however, with some elongation into rods being more prevalent for C(14)E(6). Similar structures were observed on the cellulose surface, but imaging was more difficult due to the soft gel-like nature of the cellulose thin film in water. This suggests that these surfactants adsorb in a cooperative fashion above the critical micelle concentration (cmc) with a similar interaction between surfactant headgroup and surface for both silica and cellulose. No evidence was seen for the penetration of surfactant molecules into the cellulose surface or any solubilization of the interface.
使用光反射法（OR）和软接触原子力显微镜成像研究了非离子表面活性剂在二氧化硅-水和纤维素-水界面上的吸附。研究表明，聚氧乙烯烷基醚 C(14)E(6)和 C(16)E(8)很容易吸附到这两个界面上。使用 OR 确定了吸附过程的动力学和平衡表面过剩。与先前的研究一致，短疏水基表面活性剂 C(14)E(6)在二氧化硅上的吸附程度大于长疏水基表面活性剂 C(16)E(8)。这种趋势在纤维素-水界面上也观察到了。使用软接触成像技术可视化了超过临界表面聚集浓度（csac）的吸附表面活性剂层的结构。在二氧化硅表面，两种表面活性剂的层结构主要显示为球形聚集体，但 C(14)E(6)更倾向于拉长为棒状。在纤维素表面也观察到了类似的结构，但由于纤维素薄膜在水中呈柔软的凝胶状，因此成像更加困难。这表明这些表面活性剂在超过临界胶束浓度（cmc）时以协同方式吸附，表面活性剂头基与二氧化硅和纤维素之间存在相似的相互作用。没有证据表明表面活性剂分子渗透到纤维素表面或界面的任何增溶。
